Methods, sub-systems and systems that reduce a mismatch error associated with an analog circuit

1. A sub-system, comprising:

an analog circuit configured to replicate a first current to produce a replicated version of the first current, and to subtract the replicated version of the first current from a second current to produce a third current; and

a mismatch correction circuit configured to produce an adjustment signal, indicative of a mismatch error associated with the analog circuit, based on a digital version of the third current;

wherein the adjustment signal is used to reduce the mismatch error associated with the analog circuit.

2. The sub-system of claim 1 , wherein:

the analog circuit comprises a current mirror that is configured to replicate the first current to produce the replicated version of the first current; and

the mismatch correction circuit comprises circuitry configured to adjust a gain of the current mirror to thereby reduce the mismatch error associated with the analog circuit.

3. The sub-system of claim 2 , wherein the mismatch correction circuit is configured to selectively adjust the gain of the current mirror by selectively connecting and/or disconnecting one or more transistors within the current mirror circuit.

4. The sub-system of claim 2 , wherein the mismatch correction circuit is configured to selectively adjust the gain of the current mirror by adjusting one or more voltages within the current mirror.

5. The sub-system of claim 2 , wherein:

the current mirror includes a chopper circuit that is driven by a chopper signal; and

the mismatch correction circuit includes

a digital amplitude demodulator configured to demodulate the digital version of the third current, using the chopper signal or a reproduced or recovered version of the chopper signal, to thereby produce a digital demodulation output; and

a digital filter configured to filter the digital demodulation output to thereby produce the adjustment signal.

6. The sub-system of claim 5 , further comprising:

an analog-to-digital converter (ADC) configured to receive the third current and to output the digital version of the third current that is provided to the digital amplitude demodulator.

7. The sub-system of claim 5 , wherein the digital amplitude demodulator comprises a multiplier configured to multiply the digital version of the third current by the chopping signal, or a recovered or reproduced version of the chopping signal, to thereby produce the digital demodulation output that is filtered by the digital filter to produce the adjustment signal.

8. The sub-system of claim 2 , wherein:

the first current comprises a current produced by one of more photo detectors;

the second current comprises a current produced by one or more further photo detectors;

the first current is applied to the current mirror; and

the current mirror produces the replicated version of the first current.

9. The sub-system of claim 8 , wherein:

the subsystem comprises an ambient light sensor (ALS) sub-system;

the first current is indicative of ambient infrared light; and

the second current is indicative of ambient visible light and the ambient infrared light;

the third current is indicative of the ambient visible light and a portion of the ambient infrared light that is proportional to the mismatch error.

10. The sub-system of claim 8 , wherein:

the first current is indicative of undesired light;

the second current is indicative of desired light and the undesired light; and

the third current is indicative of the desired light and a portion of the undesired light that is proportional to the mismatch error.

11. The sub-system of claim 1 , wherein the sub-system is part of a system, and wherein the mismatch correction circuit is selectively employed in accordance with at least one of the following:

during power-up of the system or the sub-system;

prior to operation of the system;

during operation of the system;

in a background of the system;

during product testing of the system or the sub-system;

periodically; or

on-demand.

12. A method for reducing a mismatch error associated within an analog circuit, comprising:

(a) accepting a first current and a second current;

(b) using the analog circuit to replicate the first current to thereby produce a replicated version of the first current, and to subtract the replicated version of the first current from the second current to thereby produce a third current;

(c) producing an adjustment signal based on a digital version of the third current, wherein the adjustment signal is indicative of the mismatch error associated with the analog circuit; and

(d) using the adjustment signal to reduce the mismatch error associated with the analog circuit.

13. The method of claim 12 , wherein the analog circuit includes a current mirror, and wherein step (d) includes using the adjustment signal to adjust a gain of the current mirror to thereby reduce the mismatch error associated with the analog circuit.

14. The method of claim 12 , wherein step (c) is performed using a digital circuit.

15. The method of claim 12 , wherein step (c) includes:

(c.1) amplitude demodulating the digital version of the third current to thereby produce a digital demodulated signal; and

(c.2) digitally filtering the digital demodulated signal to thereby produce the adjustment signal.

16. The method of claim 12 , wherein:

the first current is indicative of undesired light;

the second current is indicative of desired light and the undesired light; and

the third current is indicative of the desired light and a portion of the undesired light that is proportional to the mismatch error.

17. The method of claim 16 , further comprising:

(e) adjusting a parameter or function in dependence on the third current or the digital version of the third current.

18. A system, comprising:

a first sub-system including

an analog circuit configured to replicate a first current to produce a replicated version of the first current, and to subtract the replicated version of the first current from a second current to produce a third current;

an analog-to-digital converter (ADC) configured to produce a digital version of the third current; and

a mismatch correction circuit configured to produce an adjustment signal, indicative of a mismatch error associated with the analog circuit, based on the digital version of the third current;

wherein the adjustment signal is used to reduce the mismatch error associated with the analog circuit; and

a second sub-system configured to be adjusted in dependence on the third current or the digital version of the third current.

19. The system of claim 18 , wherein:

the first sub-system comprises an ambient light sensor (ALS) sub-system; and

the second sub-system comprises a display that is configured to have its brightness adjusted in dependence on the third current or the digital version of the third current.

20. The system of claim 18 , wherein the system, which includes the first and second sub-systems, comprises at least one of the following:

a mobile phone;

a personal data assistant;

a tablet computer;

a laptop computer;

a media player;

a media recorder;

a television; or

a gaming module.